Safety Precautions, Aircraft & Workshop
Safe working with electricity, gases, oils and chemicals; classes of fire and the correct extinguishing agent for each; action on discovering a fire.
Safety precautions, summary notes
- Safe working covers electricity, gases, oils and chemicals, and the correct response to fire. The aircraft must be made safe before work starts: electrical power isolated, systems depressurised, warning notices and ground locks fitted, and the area cordoned where needed.
- Fires are classified by the material burning. Class A solids take water or foam; Class B flammable liquids take foam, CO₂ or dry powder; Class C gases require the supply to be isolated first; Class D metals need a special dry powder; Class F cooking oils need wet chemical.
- Fires in live electrical equipment are NOT a separate class, electricity is an ignition source, not a fuel. Use CO₂ or dry powder, isolate the power, and never water or foam, which conduct.
- Wheel and brake fires take dry powder, never water, water on an overheated assembly can flash to steam and burst it. Approach fore and aft, never in line with the axle, because a fusible plug or wheel can fail explosively.
- Oxygen supports combustion and reacts violently with oil and grease, so oxygen equipment must be scrupulously clean and only approved lubricants used. Nitrogen is inert but asphyxiates by displacing air in confined spaces.
- Electrical safety: isolate and prove dead, treat capacitors and CRTs as charged after shutdown, and never work alone on high-energy systems.
- ⚠ Exam trap: water on an electrical or brake fire is the classic wrong answer, and CO₂ in a confined space is itself an asphyxiation hazard.
- Fire classes
- A solids · B liquids · C gases · D metals · F cooking oils
- Agent rule
- electrical → CO₂ / dry powder · wheels & brakes → dry powder · never water on either
A fire starts in an energised avionics rack. State the agent and the first action.
Isolate the electrical power, then use CO₂ or dry powder. Water and foam conduct and would endanger the operator; removing the ignition source is as important as applying the agent.
Why must a technician approach a suspected overheated brake unit from fore and aft rather than from the side?
An overheated wheel can fail explosively, and the debris is thrown outward along the axle line. Approaching fore and aft keeps the technician out of that path; the fusible plugs are designed to deflate the tyre before it bursts, but the approach discipline still applies.
Safety precautions concept map
Safety Precautions
Safety precautions quiz
Safety Precautions, quiz
1. Which extinguishing agent must NOT be used on an energised electrical fire?
WaterCO₂Dry powder2. Class A fires involve:
Solid combustibles such as wood and trimFlammable liquidsCombustible metals3. Class B fires involve:
Flammable liquids such as fuel and hydraulic fluidOrdinary combustible solids such as wood, paper, textiles and most plastic mouldingsFlammable gases such as propane and acetylene, whether escaping under pressure or already alight4. The correct agent for a wheel and brake fire is:
Dry powderWaterFoam5. An overheated wheel assembly should be approached:
Fore and aftIn line with the axleFrom directly above6. Fires in live electrical equipment are:
Not a separate class, electricity is an ignition sourceClass C in every standardClass D7. Class D fires involve:
Combustible metals such as magnesiumCooking oilsSolids8. Oxygen equipment must be kept free of oil and grease because:
Oxygen and hydrocarbons can ignite violentlyOil blocks the regulatorGrease absorbs oxygen9. The principal hazard of nitrogen in a confined space is that it:
Displaces air and asphyxiatesIs flammableIs corrosive10. Before disconnecting a high-pressure gas component you must:
Depressurise the systemWear gloves onlyWarm the cylinder11. The first action on discovering a fire in an energised system is to:
Raise the alarm and isolate the power where safeFind a fire blanketOpen all doors for ventilation12. When using CO₂ in a confined space the additional hazard is:
AsphyxiationElectrocutionCorrosion of structure